Virtual Inertia Control for Frequency Stabilization in a Shipboard Microgrid
Implementing virtual synchronous generator control for grid-connected converters
M. Peeters (TU Delft - Electrical Engineering, Mathematics and Computer Science)
J. Dong – Mentor (TU Delft - Electrical Engineering, Mathematics and Computer Science)
J. Dong – Graduation committee member (TU Delft - Electrical Engineering, Mathematics and Computer Science)
F.A. Muñoz Muñoz – Graduation committee member (TU Delft - Electrical Engineering, Mathematics and Computer Science)
Peter Roodnat – Mentor
Marcel Zevenbergen – Mentor
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Abstract
Shipboard microgrids are inherently weak systems due to their limited inertia and high impedance, making them prone to voltage and frequency fluctuations during faults and load changes. These challenges are further intensified by highly dynamic load conditions and the ongoing hybridization of shipboard power systems, where conventional diesel generators, functioning as synchronous generators, are increasingly being replaced by renewable energy sources (RES) and energy storage systems (ESS). As a result, the overall rotational inertia of the system is reduced, degrading its frequency stability.
This thesis proposes a method to emulate inertia using an ESS by implementing a virtual synchronous generator (VSG) control scheme. The ESS, interfaced through a power converter connected to the microgrid, replicates the kinetic energy behavior of a synchronous generator, providing both frequency and voltage support. A detailed Simulink model of a shipboard microgrid was developed, including converters, loads, synchronous generators, and grid-connected and islanded configurations. The VSG control scheme was designed and tuned based on system parameters, and its performance was evaluated through simulations and experimental testing.
Results demonstrate that a VSG control scheme based on the swing equation successfully provides virtual inertia, improving frequency stability by improving the frequency nadir and reducing the rate of change of frequency (RoCoF) by 85\%. In addition, the integration of integral Q–U droop control effectively regulates voltage, ensuring deviations remain within acceptable limits. The proposed control strategy is particularly beneficial for load variations exceeding 1 kVA/s and maintains stable operation even in islanded mode when synchronous generators are disconnected.
The study also identifies key design trade-offs, including the balance between frequency settling time and nadir, as well as between RoCoF reduction and power oscillations, which are influenced by the damping and inertia parameters. Similarly, voltage performance depends on the tuning of reactive power droop parameters, affecting both voltage deviation and dynamic response.
In conclusion, the use of VSG-based virtual inertia significantly enhances the stability of low-inertia shipboard microgrids, particularly in the context of increasing system hybridization. Future work should focus on optimal ESS selection, higher-level energy management strategies, and adaptive tuning of control parameters.